JP2002108076A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent write defect of an electrostatic latent image caused by the adhesion of fogging toner which remains in the non-image region of both ends of a developing means after imaging on a write electrode. SOLUTION: In the image forming apparatus which forms an electrostatic latent image on an image carrier by an electrostatic charge write means 3 having a plurality of write electrodes coming in contact with or disposed closely to the image carrier along the axial direction of the image carrier 2, when the image carrier contact width of the above electrostatic charge write means is expressed as L1, a toner carrying width opposed to the image carrier of a developing means is expressed as L2, the width of the image carrier is expressed as L0 and the width of a transfer means is expressed as L3, the relations of L1<L2 and L1<L3 are satisfied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming method in which a base material of a charging and writing apparatus is brought into elastic contact with an image carrier and a latent image is formed on the image carrier by a writing electrode provided on the base material. Related to the device.

[0002]

2. Description of the Related Art Conventionally, there has been known an image forming apparatus which forms an electrostatic latent image on an image carrier using a large number of needle electrodes. In this multi-needle electrode system, an electrostatic latent image is formed on an image carrier by discharging from a needle electrode, and therefore, a needle electrode having the lowest discharge start voltage is used for a discharge portion, and this is an image. It is desirable that the tip is sharp in order to improve the resolution. Generally, the needle electrode and the image carrier are arranged in a non-contact manner with a small gap, and an electrostatic latent image is formed on the image carrier by a discharge phenomenon.

[0003] However, variations in the discharge start voltage due to gap variations directly result in variations in the potential of the electrostatic latent image, leading to serious image defects such as streak unevenness, image discontinuity, blurring, and dust. Therefore, in order to stably keep the gap constant, the needle electrode needs to have high precision and high rigidity, and the holding member for positioning and supporting the needle electrode also needs to have high precision and high rigidity.
Furthermore, unless the needle electrode is accurately positioned on the generatrix of the image carrier in the circumferential direction of the image carrier, the gap changes and uniform charging cannot be performed. In addition, spacers and the like are added to manage the gap in order to reliably change the gap due to the rotational fluctuation of the image carrier.However, in high-speed printing where the image carrier rotates at high speed, the gap can be kept constant by vibration or the like. However, as a result, the printing speed was kept low.

To solve these problems, Japanese Unexamined Patent Publication No.
JP-45104A proposes that a needle electrode is brought into contact with an image carrier coated with inorganic glass, and further, lubricating oil is applied to the image carrier to prevent wear damage of the needle electrode to the image carrier. I am doing.

[0005]

However, in Japanese Unexamined Patent Publication No. 63-45104, the wear of the needle electrode occurs, the discharge starting voltage fluctuates, and the size of the electrostatic latent image and the charging potential fluctuate. Have the problem of Further, since the configuration in which oil is applied to the image carrier is an essential requirement for reducing wear, toner and the like cannot be directly developed, and the image carrier can be used only as an intermediate image carrier.

As described above, the multi-needle electrode system has a problem that the image quality is deteriorated because the potential of the electrostatic latent image easily varies and the resolution of the electrostatic latent image also changes with time. A high-precision holding member and a positioning member for positioning and a gap with the carrier are required, which causes a problem that the device becomes complicated and large. In addition, since the contact pressure is high due to the needle electrode, there is a problem that the electrode and the image carrier are damaged in a short time, it is difficult to speed up printing, and the device is enlarged as it is used as an intermediate image carrier. There is a problem that.

In order to solve this problem, the present applicant has
There has been proposed an image forming apparatus in which a base material of a charged writing device is brought into elastic contact with an image carrier, and an electrostatic latent image is formed on the image carrier by a writing electrode provided on the base material. According to this image forming apparatus, when an electrostatic latent image is formed on an image carrier by sending a write signal to the electrode portion, the contact between the substrate and the image carrier is stabilized, and uniform charging and writing is performed. And a good image without image unevenness or streaks can be obtained.

However, the image forming apparatus has the following problems. This will be described with reference to FIGS.

[0009] As shown in FIG.
In order to stabilize the contact between the end electrode 3bR of the writing electrode 3b and the base electrode 3a, the length L of the end electrode 3bR and the end of the base material 3a
Need to be secured for a long time. If L is not secured, the contact pressure of the electrode near the end electrode 3bR with the image carrier 2 becomes smaller than that of the writing electrode at the center, and uniform charging and writing cannot be performed. On the other hand, at the contact interface between the toner regulating member 4c of the developing device 4 and the end sealing material 4d, the toner cannot be completely sealed as shown in FIG. And adheres to the image carrier 2.
However, by increasing the length L,
The edge leakage toner T adheres to the contact portion between the writing electrode 3b and the image carrier 2 via the lower surface of the base material 3a, and the gap between the electrode and the image carrier 2 fluctuates. Will appear.

In order to prevent this, as shown in FIG. 8, the width of the charge writing means 3 is set to be smaller than the width of the toner regulating member 4c. In this case, the width of the transfer roller of the transfer device 6 needs to have a width in consideration of the conveyance accuracy for the maximum recording sheet. Further, in order to prevent the end portion leakage toner T from adhering to the transfer roller, the transfer roller width needs to be smaller than the toner regulating blade 4c. The width of the image carrier 2 needs to be set so as to be the largest with respect to the other members in order for the respective members to stably abut. As described above, when the width dimension of each member is set, the fog toner adheres to the transfer roller in the area α between the end of the maximum recording sheet and the end of the transfer roller, and the end of the transfer roller and the toner regulating blade. 4c, the fog toner remains on the image carrier 2 even after the transfer to the recording sheet. Then, the fog toner in the area γ between the end of the transfer roller and the end of the charging writer 3 is slightly attached to the end of the charging writer 3, and the write electrode 3 b near the end abuts. Becomes unstable with time, the gap between the electrode and the image carrier 2 fluctuates, and the image becomes uneven.

The present invention has been made to solve the above problems, and a first object of the present invention is to stabilize the potential and size of an electrostatic latent image and form a high-resolution and high-quality image. A second object is to reduce the wear of the electrodes and the image bearing member and improve the durability. The second object is that the fogging toner remaining on the non-image areas at both ends of the developing means adheres to the writing electrode. An object of the present invention is to prevent a writing failure of the generated electrostatic latent image.

[0012]

According to a first aspect of the present invention, there is provided an image forming apparatus including a plurality of writing electrodes which are in contact with or close to an image carrier along an axial direction of the image carrier. In an image forming apparatus for forming an electrostatic latent image on an image carrier by a charging writer, the image bearing member contact width of the charging writer is set to L1, and the toner carrying width of the developing device facing the image carrier is set to L1. L2, L1 <L2 and L1 <L3, where L0 is the width of the image carrier and L3 is the width of the transfer unit.
The invention according to claim 2 is characterized in that the relationship of L1 <L3 <L2 is satisfied.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of an image forming apparatus according to the present invention, and FIG.
FIG. 2B is a partial perspective view of the image carrier and the charge writing device of FIG. In the following description, the same components are denoted by the same reference numerals in the drawings, and the description may be omitted.

Referring to FIG. 1A, an image forming apparatus 1 according to the present invention includes an image carrier 2 on which an electrostatic latent image is formed, and an image carrier 2 that contacts the image carrier 2 and electrostatically contacts the image carrier 2. A charging / writing device 3 for writing a latent image, a developing device 4 for developing an electrostatic latent image on the image carrier 2 with a developer, and a toner image on the image carrier 2 developed by the developing device 4 on paper And the like, and a cleaning device 7 for removing the toner remaining on the image carrier 2 after the transfer. One end of the charging writing device 3 is supported by the fixed portion 9 in a cantilever manner, and the other end is in contact with the image carrier 2.

As shown in FIG. 1B, the charge writing device 3
Is a flexible base material 3a having high insulation properties, such as FPC (Flexible Print Circuit) or PET film, which is relatively soft and elastic, and a weak elastic material which is formed on the base material 3a and which is bent by the base material 3a. Write electrode 3 which is lightly pressed onto image carrier 2 by restoring force and arranged in contact or close proximity
b. The driver 3 is provided on the substrate 3a.
c, a conductive pattern 3d is formed and connected to the write electrode 3b. Note that the pressing force of the writing electrode 3b is 300
mm and a pressing force of 10 N or less, that is, a linear pressure of 0.33 N / m
m or less stabilizes contact and injects or discharges (voids)
It is preferable in terms of stabilization, and from the viewpoint of abrasion, it is desirable to reduce the linear pressure as much as possible while maintaining a state in which the contact is kept stable.

FIGS. 2 and 3 show the charged writing device 3 of FIG.
2 (A) is an enlarged view of a contact portion between the writing electrode 3b and the image carrier 2, and FIG. 2 (C) to 2 (F) show the relationship between each parameter and the surface potential of the image carrier 2, and FIG. 3 (A) shows the image carrier by charge injection. FIG. 3 (B) is an explanatory view of charging the body.
FIG. 3 is a view for explaining charging of the image carrier by discharging, and FIG.
(C) is a diagram for explaining Paschen's law.

As shown in FIG. 2A, the image carrier 2 is made of a conductive material such as aluminum, and has a grounded base 2c and an insulating property formed on the outer periphery of the base 2c. And a charging layer 2d. Writing electrode 3 supported on base material 3a made of FPC or the like of charged writing device 3
b is in contact with the charging layer 2d with a predetermined light pressing force as described above, and the image carrier 2 is moving (rotating) at a predetermined speed v. A predetermined high voltage V is applied to the write electrode 3b.
₀ or a predetermined low voltage V ₁ is adapted to be applied selectively switched through the substrate 3a.

That is, an electrical equivalent circuit shown in FIG. 2B is formed on the contact surface (nip portion) between the writing electrode 3b and the image carrier 2. In FIG. 2B, R
Indicates the resistance of the writing electrode 3b, and C indicates the capacitance of the image carrier 2. Resistance R of the writing electrode 3b is the A side - is adapted to be selectively switched for connection to a predetermined voltage V ₀ or the ground voltage V ₁ of the B-side ().

[0019] In the equivalent circuit, by connecting the writing electrode 3b to the A side to the writing electrode 3b (-) of the writing electrode 3b upon application of the predetermined voltage V ₀ which resistor R and the image carrier 2 As shown by the solid line in FIG. 2C, the surface potential of the image carrier 2 is constant at a predetermined voltage V _{0 in a} region where the resistance R of the writing electrode 3b is small, as indicated by the solid line in FIG. If the resistance R is larger than a predetermined value, the absolute value of the surface potential of the image carrier 2 decreases. On the other hand, when the write electrode 3b is connected to the B side and the write electrode 3b is grounded, the relationship between the resistance R of the write electrode 3b and the surface potential of the image carrier 2 is shown in FIG.
Approximately ground voltages V ₁ becomes the surface potential of the resistor R is small in a region of the image carrier 2 the writing electrode 3b as indicated by the dotted line is constant, the resistance R of the writing electrode 3b is a larger area than a predetermined value Then, the absolute value of the surface potential of the image carrier 2 increases.

[0020] In the area resistance R is small predetermined voltage V ₀ or constant ground voltages V ₁ the surface potential of the constant image carrier 2 of the writing electrodes 3b, the image as shown in FIG. 3 (A) Between the writing electrode 3b in contact with the carrier 2 and the charged layer 2d of the image carrier 2, charge injection of (-) charge is performed directly from the lower voltage to the higher voltage, and the image carrier 2 is charged. Is charged. Further, the resistance R of the writing electrode 3b is large,
In the region where the surface potential starts to change, the charge of the image carrier 2 due to the charge injection gradually decreases, and the resistance R of the writing electrode 3b increases, as shown in FIG. Discharge starts to occur between the image carrier 3a and the image carrier 2.

The discharge between the substrate 3a and the substrate 2c of the image carrier 2 occurs when the voltage between the substrate 3a and the image carrier 2 becomes higher than the discharge starting voltage. Lumber 3
a and the gap between the image carrier 2 and the discharge starting voltage V
The relationship with _th is as shown in FIG. 3C according to Paschen's law. That is, when the gap is about 30 μm, the discharge starting voltage V _th is the smallest, and the gap is about 30 μm.
Regardless of whether it is smaller or larger than μm, the discharge starting voltage _Vth increases, and it becomes difficult for discharge to occur. This discharge also charges the surface of the image carrier 2. However, when the resistance R of the writing electrode 3 is in this region, the charge of the image carrier 2 due to charge injection is large, and the charge of the image carrier 2 due to discharge is small. Is dominant. In charging by the charge injection, the surface potential of the image carrier 2 becomes to the predetermined voltage V ₀ or the ground voltage V ₁ applied to the writing electrode 3b. In the case of charging by charge injection, it is desirable that the predetermined voltage V ₀ supplied to the writing electrode 3 b is set to be equal to or lower than a discharge starting voltage V _{th at which} a discharge occurs between the writing electrode 3 b and the image carrier 2.

In a region where the resistance R of the writing electrode 3b is larger, the charge of the image carrier 2 due to charge injection is small, and the charge of the image carrier 2 due to discharge becomes larger than the charge due to charge injection. In the charging of No. 2, charging by discharge gradually becomes dominant. That is, the resistance R of the write electrode 3b
Is larger, the surface of the image carrier 2 is charged mainly by electric discharge, and the image carrier 2 is hardly charged by charge injection. In or removal of charge by the discharge, the surface potential of the image carrier 2 becomes a voltage obtained by subtracting the discharge starting voltage V _th from the predetermined voltage V ₀ or ground voltages V ₁ is applied to the writing electrode 3b. The same applies to the case where the predetermined voltage V ₀ is a voltage of (+).

Therefore, the resistance R of the electrode 3b is changed to a predetermined voltage | V ₀ | (the surface voltage of the image carrier 2 is constant) or a constant ground voltage V
₁ and a small area, and the write electrode 3b
Is controlled between the predetermined voltage V ₀ and the ground voltage V ₁ to charge the image carrier 2 by charge injection.

Further, the write electrode 3b is connected to the A side to
A predetermined voltage V of (-) is applied to the write electrode 3b. ₀When applying
Relationship between capacitance C of image carrier 2 and surface potential of image carrier 2
Indicates that the capacitance C is small, as indicated by the solid line in FIG.
In the range, the surface potential of the image carrier 2 is constant at a predetermined voltage V₀Tona
In a region where the capacitance C is larger than a predetermined value,
The absolute value of the surface potential decreases. On the other hand, the write electrode 3b is set to B
Image bearing when this writing electrode 3b is grounded by connecting
The relationship between the capacitance C of the body 2 and the surface potential of the image carrier 2 is shown in FIG.
As shown by the dotted line in (D), the capacity C of the image carrier 2 is small.
In the region, the surface potential of the image carrier 2 is substantially constant and substantially equal to the ground voltage V.
₁Where the capacity C of the image carrier 2 is larger than a predetermined value.
Then, the absolute value of the surface potential of the image carrier 2 increases.

Then, in a region where the capacitance C of the image carrier 2 is small and the surface potential of the image carrier 2 is a constant predetermined voltage V ₀ or a constant ground voltage V ₁ , the writing electrode contacting the image carrier 2 Charge injection of (-) charges is performed directly between 3b and the charging layer 2d of the image carrier 2. That is, the image carrier 2 is charged by charge injection. In a region where the capacitance C of the image carrier 2 is large and the surface potential of the image carrier 2 starts to change, the charge of the image carrier 2 due to charge injection gradually decreases, and the capacitance C of the image carrier 2 decreases. As shown in FIG. 3B, the base material 3a and the image carrier 2
And a discharge is caused to occur between them. This discharge also charges the surface of the image carrier 2. However, when the capacity C of the image carrier is in this area, the charge of the image carrier 2 due to the charge injection is large and the charge of the image carrier 2 due to the discharge is small, and the charge of the image carrier 2 is dominated by the charge due to the charge injection. It has become a target. In charging by the charge injection, the surface potential of the image carrier 2 becomes to the predetermined voltage V ₀ or the ground voltage V ₁ applied to the writing electrode 3b.

In a region where the capacitance C of the image carrier 2 is even larger, this charge is hardly injected between the writing electrode 3b and the charged layer 2d of the image carrier 2. That is, the image carrier 2 is not charged by the charge injection. The same applies to the case where the predetermined voltage V ₀ is a voltage of (+).

Therefore, the capacitance C of the image carrier 2 is set to a small area where the surface potential of the image carrier 2 becomes a constant predetermined voltage | V ₀ | or a constant ground voltage V _1, and the writing electrode 3b is set. Is controlled between the predetermined voltage V ₀ and the ground voltage V ₁ to charge the image carrier 2 by charge injection.

Further, the write electrode 3b is connected to the A side to
A predetermined voltage V of (-) is applied to the write electrode 3b. ₀When applying
Velocity (peripheral speed) V of image carrier 2 and surface potential of image carrier 2
As shown by the solid line in FIG.
In a region where the velocity v of the image carrier 2 is relatively small,
The potential increases as the speed v increases, and the image bearing
When the speed v of the body 2 becomes larger than a predetermined value,
The absolute value of the surface potential is a constant voltage. Table of image carrier 2
The surface potential increases as the speed v of the image carrier 2 increases.
Shows an image caused by friction between the writing electrode 3b and the image carrier 2.
Facilitating charge injection by friction of the carrier 2
It is thought to be due to. Charge due to this friction
In order to facilitate the insertion, the speed v of the image carrier 2 is increased to some extent.
And does not change, and becomes almost constant. On the other hand, the write electrode 3b is
Speed when the write electrode 3b is connected to the B side and the write electrode 3b is grounded
The relationship between v and the surface potential is shown by the dotted line in FIG.
Constant ground voltage V regardless of speed v₁Becomes In addition,
Predetermined voltage V₀The same applies to the case where is a voltage of (+).

Further, the write electrode 3b is connected to the A side to
A predetermined voltage V of (-) is applied to the write electrode 3b. ₀When applying
The pressing force of the writing electrode 3b against the image carrier 2 (hereinafter simply referred to as writing
(Referred to as the pressure of the electrode 3b) and the surface potential of the image carrier 2.
The relation is as shown by the solid line in FIG. 2 (F).
In a region where the force is extremely small, the surface potential of the image carrier 2 is
As the pressure of the writing electrode 3b increases, it becomes relatively sharp.
Rises, and the pressure of the writing electrode 3b becomes larger than a predetermined value.
And the absolute value of the surface potential of the image carrier 2 becomes a constant voltage.
You. The surface potential of the image carrier 2 increases the pressure of the writing electrode 3b.
Rise rapidly according to the writing electrode 3 b and the image carrier 2.
Contact becomes more reliable as the pressure of the write electrode 3b increases.
It is thought to be the result. This writing
The reliability of the contact between the electrode 3b and the image carrier 2 depends on the writing electrode 3
When the pressure of b becomes large to some extent, it does not change and is almost constant
Becomes On the other hand, by connecting the write electrode 3b to the B side,
Pressure and image bearing of writing electrode 3b when electrode 3b is grounded
The relationship with the surface potential of the body 2 is shown by a dotted line in FIG.
The constant ground voltage V is independent of the pressure of the write electrode 3b.₁
Becomes The predetermined voltage V₀Even if the voltage is (+)
The same is true.

In this way, the resistance R of the writing electrode 3b and the capacitance C of the image carrier 2 are set so that the surface potential of the image carrier 2 becomes a constant predetermined voltage, and the image carrier 2
And the pressure of the writing electrode 3b are controlled so that the surface potential of the image carrier 2 becomes a constant predetermined voltage.
Switching control of the voltage applied to b between the predetermined voltage V ₀ and the ground voltage V ₁ makes it possible to reliably and easily charge the image carrier 2 by charge injection.

FIG. 4 shows that the plurality of writing electrodes 3b are
FIG. 7 is a diagram showing an example of an array pattern when the pixels are arranged in the axial direction of FIG.

The simplest arrangement pattern of the plurality of write electrodes 3b is one in which a plurality of rectangular write electrodes 3b are arranged in a line in the axial direction of the image carrier 2 as shown in FIG. is there. In this case, among the plurality of writing electrodes 3b, driving control by switching the writing electrodes 3b writing electrode 3b is their respective predetermined number (eight in the illustrated example) to a predetermined voltage V ₀ or ground voltages V ₁ The plurality of sets are connected to one driver 3c, and a plurality of the sets are arranged in a line in the axial direction of the image carrier 2.

However, when the write electrodes 3b are simply arranged in a line in the axial direction of the image carrier 2, crosstalk between adjacent write electrodes 3b may occur. Therefore, in the example shown in FIG. 4B, the write electrodes 3b are arranged in two rows and in a zigzag manner in a direction orthogonal to the axial direction of the image carrier 2, and the row interval between the write electrodes 3b is increased. The crosstalk between the electrodes is reduced.

FIG. 5 is a diagram showing a switching circuit for switching and connecting predetermined voltage V ₀ and ground voltage V ₁ to write electrode 3b. As shown in FIG. 5, for example, the write electrodes 3b arranged in four rows are respectively connected to corresponding high voltage switches (HVSW) 15, and these high voltage switches 15 are respectively ,
To the corresponding electrode 3b and the predetermined voltage V ₀ and the ground voltages V ₁ is adapted to switch connection. An image writing control signal from a shift register (SR) 16 is input to each of the high voltage switches 15.
, The image signal stored in the buffer 17 and the clock signal from the clock 18 are input.
Then, the image write control signal from the shift register 16 is input to each high voltage switch 15 by the AND circuit 19 based on the write timing signal from the encoder 20. Each high voltage switch 15 and AND circuit 1
9 constitutes the above-described driver 3c for switching and controlling the supply voltage to each write electrode 3b.

FIG. 6 shows each high voltage switch 1 of each electrode 3b.
5 to each predetermined voltage V ₀ or ground voltages V ₁ selectively illustrates a state when the switch control, FIG. 6 (A) shows the voltage state of the electrodes, FIG. 6 (B) FIG. 6 (A FIG. 6C is a diagram illustrating a developer image when normal development is performed in the voltage state of FIG. 6C, and FIG. 6C is a diagram illustrating a developer image when reverse development is performed in the voltage state of FIG.

As shown in FIG. 6, for example, the (n-2) th, n
-1st, nth, n + 1th, n + 2th electrodes 3
In FIG. 6B, it is assumed that the respective high-voltage switches 15 are switched and controlled to be in the voltage state shown in FIG. Therefore, when the electrostatic latent image is written on the latent image carrier 2 by each electrode in such a voltage state and the electrostatic latent image is developed by regular development, the developer 8 Predetermined voltage V
_The developer image adheres on the ₀ portion, and a developer image as shown by hatching in FIG. 6B is obtained. Further, performs writing of an electrostatic latent image in the same manner, when developing the electrostatic latent image by reversal development, the developer 8 is deposited on the ground voltages V ₁ part of the latent image carrier 2, FIG. 6 ( A developer image as shown by hatching in C) is obtained.

According to the image forming apparatus 1 using the charging writing device 3 configured as described above, the writing electrode 3b is connected to the base 3a.
The writing electrode 3b can be stably contacted with the latent image carrier 2 because the writing electrode 3b is brought into contact with the latent image carrier 2 with a small pressing force due to the small elastic restoring force. Therefore, the latent image carrier 2 can be more stably and highly accurately charged by the writing electrode 3b. Thereby, the writing of the electrostatic latent image can be performed more stably, so that a good image can be obtained reliably and with high accuracy.

Further, since the writing electrode 3b is merely brought into contact with the latent image carrier 2 with a small pressing force, the writing electrode 3b
Can prevent the latent image carrier 2 from being damaged, and the durability of the latent image carrier 2 can be improved. Furthermore, since only the writing electrode 3b is used as the writing device 3 and a large laser light generating device or an LED lamp light generating device as in the related art is not provided, the size of the device can be further reduced. As a result, the number of parts can be further reduced, and a simpler and less expensive image forming apparatus can be obtained. Further, generation of ozone can be further suppressed by the writing electrode 3b.

FIGS. 7 and 8 are views for explaining the problem of the present invention. FIG. 7A is a perspective view showing an example of an image forming apparatus using a charge writing device, and FIG. ) Is FIG.
8A is a partial cross-sectional view, and FIG. 8 is a diagram for explaining the width dimension of each member.

As shown in FIG. 7A, the charge writing device 3
In order to stabilize the contact between the end electrode 3bR of the writing electrode 3b and the base electrode 3a, the length L of the end electrode 3bR and the end of the base material 3a
Need to be secured for a long time. If L is not secured, the contact pressure of the electrode near the end electrode 3bR with the image carrier 2 becomes smaller than that of the writing electrode at the center, and uniform charging and writing cannot be performed. On the other hand, at the contact interface between the toner regulating member 4c of the developing device 4 and the end sealing material 4d, the toner cannot be completely sealed as shown in FIG. And adheres to the image carrier 2.
However, by increasing the length L,
The edge leakage toner T adheres to the contact portion between the writing electrode 3b and the image carrier 2 via the lower surface of the base material 3a, and the gap between the electrode and the image carrier 2 fluctuates. Will appear.

In order to prevent this, as shown in FIG. 8, the width of the charge writing means 3 is set to be smaller than the width of the toner regulating member 4c. In this case, the width of the transfer roller of the transfer device 6 needs to have a width in consideration of the conveyance accuracy with respect to the maximum recording sheet. Further, in order to prevent the end portion leakage toner T from adhering to the transfer roller, the transfer roller width needs to be smaller than the toner regulating blade 4c. The width of the image carrier 2 needs to be set so as to be the largest with respect to the other members in order for the respective members to stably abut. As described above, when the width dimension of each member is set, the fog toner adheres to the transfer roller in the area α between the end of the maximum recording sheet and the end of the transfer roller, and the end of the transfer roller and the toner regulating blade. 4c, the fog toner remains on the image carrier 2 even after the transfer to the recording sheet. Then, the fog toner in the area γ between the end of the transfer roller and the end of the charging writer 3 is slightly attached to the end of the charging writer 3, and the write electrode 3 b near the end abuts. Becomes unstable with time, the gap between the electrode and the image carrier 2 fluctuates, and the image becomes uneven.

In order to solve the above problems, embodiments of the present invention will be described in detail. FIG. 9 is a diagram illustrating an embodiment of the image forming apparatus according to the present invention and illustrating a width dimension of each member.

The base material 3a of the charging writing means 3 includes a writing electrode 3
In order to stabilize the contact between the end electrode 3bR and the end electrode 3bR, the length L of the end electrode 3bR and the end of the base material 3a is ensured to be long, and the width of the charging / writing means 3 is adjusted to the width of the transfer roller of the transfer means 6. Smaller than the width. The transfer roller width needs to have a width dimension that takes into account the transport accuracy of the maximum recording sheet. Further, the width of the transfer roller is set smaller than the toner regulating blade 4c in order to prevent the end portion leakage toner T from adhering to the transfer roller. The width of the image carrier 2 is set so as to be the largest with respect to the other members in order for the respective members to stably abut.

As described above, since the width of each member is set, the fogging toner generated in the area α between the end of the maximum recording sheet and the end of the transfer roller can adhere to the transfer roller. Further, the fog toner generated in the area β between the end of the transfer roller and the end of the toner regulating blade 4c remains on the image carrier 2 even after the transfer to the recording sheet.
There is no effect on the charge writing means 3. As described above, since the width of the charge writing unit 3 is set smaller than the width of the transfer roller of the transfer unit 6, the area of γ described in FIG.
Therefore, the toner remaining in the non-image areas at both ends of the developing means 4 is prevented from adhering to the ends of the charging and writing means 3.

To summarize the above relationship, as shown in FIG. 9, the image bearing member contact width dimension of the charge writing means 3 is L1, the toner carrying width of the developing means 4 opposed to the image carrier is L2, Assuming that the width of the carrier 2 is L0 and the width of the transfer means 6 is L3, it is only necessary to satisfy the relations of L1 <L2 and L1 <L3. Further, preferably, L1 <L3 <
What is necessary is to satisfy the relationship of L2.

FIG. 11 shows an example in which the present invention is applied to an image forming apparatus using the intermediate transfer belt 25. The image bearing member contact width of the charging / writing means 3 is L1, and the image bearing member of the developing means 4 is shown. L2 <L2, the width of the image carrier 2 is L0, and the width of the transfer unit 6 is L3.
2 and L1 <L3. More preferably, the relationship of L1 <L3 <L2 may be satisfied.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications can be made. Hereinafter, a specific example of an image forming apparatus using the writing device of the present invention for writing an electrostatic latent image by bringing the electrode portion 3b into contact with the image carrier 2 will be described.

FIG. 12 is a diagram schematically showing another example of an image forming apparatus using the writing device of the present invention. This image forming apparatus 1 is an image forming apparatus that performs full-color development by superimposing four colors of black K, yellow Y, magenta M, and cyan C on an image carrier 2, and is an endless belt-shaped image carrier. 2 is provided. The endless belt-shaped image carrier 2 is stretched between two rollers 22 and 23,
Of these, the roller on the driving side rotates clockwise in the figure.

Along the straight portion of the endless belt of the image carrier 2
And a writing device 3 for each color._K, 3 _Y, 3_M, 3_Cand
Developing device 4_K, 4_Y, 4_M, 4_CIs upstream of the image carrier 2 in the rotation direction.
Colors K, Y, M, and C are arranged in this order from the side. Rice cake
These developing devices 4_K, 4_Y, 4 _M, 4_CIs not shown
It is also possible to arrange them in the following order. Writing device for each color
3_K, 3_Y, 3_M, 3_CEach of the electrodes 3b is as described above.
And lightly contact the image carrier 2 with a small pressing force. Note that
Although not shown, the image forming apparatus 1 of this example also
Endless belt writing device 3 for carrier 2_K, 3_Y, 3_M, 3_CAnd anti
The above-mentioned image carrier uniform charge control device is provided on the opposite straight section.
Have been.

In the image forming apparatus 1 of this embodiment thus configured, the surface of the image carrier 2 is uniformly charged by the image carrier uniform charging control device as described above. Thereafter, the electrostatic latent image of black K is written on the surface of the image bearing member in the electrode 3b _K of the writing device 3 _K of first black K, the electrostatic latent image of the black K is then developed by the developing device 4 _K Thus, a black K developer image is formed on the surface of the image carrier 2. Then, along with the electrostatic latent image for cyan C is written on top of the developer image on the surface to and black K of the image carrier 2 _C by electrodes 3b _C of the writing device 3 _C of cyan C, the cyan C an electrostatic latent image developer image cyan C the developed in the surface of the image carrier 2 by the developing apparatus 4 _C is formed of. Similarly, after the electrostatic latent image of magenta M is written on top of each developer image on the image bearing member 2 and the black K and cyan C by electrodes 3b _M of the writing device 3 _M of magenta M, The magenta M electrostatic latent image is developed by the developing device 4 _M to form a magenta M developer image on the surface of the image carrier 2 and on each of the black K and cyan C developer images.
After the electrostatic latent image for cyan C is written on top of each developer image on the image bearing member 2 and the black K and cyan C and magenta M by the electrodes 3b _C of the writing device 3 _C, the cyan C an electrostatic latent image is color matching is developer image cyan C is formed on each developer image on the surface and black K and cyan C and magenta M of being developed by the developing device 4 _C image carrier 2,
Thereafter, these developer images are transferred by the transfer device 6 to the transfer material 5.
Then, a full-color developer image in which the developer images of the respective colors are color-matched is formed.

As described above, the developer image of each color is transferred to the image carrier 2.
Even in a full-color image forming apparatus in which the colors are superimposed on each other, a smaller and simpler configuration can be obtained by using the writing device 3 of the present invention.

FIG. 13 shows an image using the writing device of the present invention.
It is a figure which shows the further another example of a forming apparatus typically. This example
Is an image forming apparatus 1 for each color._K, 1_C, 1
_M, 1 _YAre in this order from the upstream side in the moving direction of the transfer material 5.
Located in tandem. Image forming apparatus 1 for each color_K, 1
_C, 1_M, 1_YCan be set in any order.
Can be. Each image forming apparatus 1_K, 1_C, 1_M, 1_YIs it
Each of the image carriers 2_K, 2_C, 2_M, 2_Y, Writing device 3_K, 3_C,
3_M, 3_Y, Developing device 4_K, 4_C, 4_M, 4_YAnd transfer device 6
_K, 6_C, 6_M, 6_YIt has. Although not shown, each image
Image forming apparatus 1_K, 1_C, 1_M, 1_YAre the image carriers, respectively.
Charging device for each color_K, 3_C, 3_M, 3_YYo
Image carrier 2_K, 2_C, 2_M, 2_YInstalled on the upstream side in the rotation direction of
Have been.

[0053] In the image forming apparatus 1 of the thus constituted this example, the image forming apparatus 1 _K of first black K, the surface of the image carrier 2 _K by the image bearing member uniformly charging control device for black K uniformly after being charged, the writing device 3 _K electrodes 3b _K electrostatic latent image is an image bearing member 2 _K of black K
With written on the surface of the electrostatic latent image of the black K developer image of black K is formed developed by the surface of the image carrier 2 _K in the developing device 4 _K. This developer image transfer apparatus 6 _K for black K on the image carrier 2 _K, is transferred to the transfer material 5 that has been supplied, the developer image of black K is formed on the transfer material 5. Next, the cyan C image forming apparatus 1
In _C, after which the surface of the image carrier 2 _C is uniformly charged by the image bearing member uniformly charging control device cyan C, an electrostatic latent image of cyan C in the electrode 3b _C of the writing device 3 _C statue Carrier 2 _C
With written on the surface of the electrostatic latent image of the cyan C is developer image cyan C the developed and the image carrier 2 _C surface of the developing device 4 _C is formed. In this image bearing member 2 developer image cyan C on _C transfer device 6 _C, are transferred to overlap the transfer material 5 on which the developer image is formed of black K, which is supplied, cyan C to the transfer material 5 Is formed. Similarly, magenta M to the image carrier 2 _M by electrodes 3b _M of the writing device 3 _M in the image forming apparatus 1 _M of magenta M
Writing of an electrostatic latent image, after developing the electrostatic latent image developing device 4 _M, where and superposed transfer of the developer image of magenta M to the transfer material 5 of the transfer device 6 _M has been performed, the yellow Y the image carrier 2 _Y by electrodes 3b _Y of the writing device 3 _Y in the image forming apparatus 1 _Y
Yellow Y writing of an electrostatic latent image on the developing device 4 development of _Y electrostatic latent image, and transferring the developer image of yellow Y to the transfer material 5 of the transfer device 6 _Y is performed, transfer A full-color developer image in which the developer images of the respective colors are color-matched on the material 5 is formed.

As described above, the image forming apparatus 1 _K , 1 _C , 1 of each color is used.
_M, 1 _Y also in that a full color image forming apparatus arranged in tandem, by using the writing device 3 of the present invention can be a simple structure more and more compact.

FIG. 14 is a view schematically showing still another example of an image forming apparatus using the writing device of the present invention. FIG.
In the image forming apparatus 1 in which the image forming apparatuses 1 _K , 1 _C , 1 _M , and 1 _Y of the respective colors are arranged in tandem, the image holding apparatuses 1 _K , 1 _C , 1 _M , and 1 _Y carry the images. The developer images of the respective colors formed on the bodies 2 _K , 2 _C , 2 _M , and 2 _Y are transferred to the transfer material 5 for each of the image forming apparatuses 1 _K , 1 _C , 1 _M , and 1 _Y. However, in the image forming apparatus 1 of this example, the image carriers 2 _K , 2 _C , 2 _M , and 2 _{Y of the} respective colors are provided.
After the developer images of each color formed on the intermediate transfer are once intermediately transferred,
The image is transferred to the transfer material 5. That is, in the image forming apparatus 1 of this example, the intermediate transfer device 24 is provided in the image forming apparatus 1 of the example shown in FIG. The intermediate transfer device 24 includes an endless belt-shaped intermediate transfer body 25. The intermediate transfer body 25 is stretched between two rollers 26 and 27, and is driven in a counterclockwise direction in FIG. It is designed to rotate.

The linear portion of the intermediate transfer body 25
Along each image forming apparatus 1_K, 1_C, 1 _M, 1_YIs arranged
And one transfer device 6 is located at the position of the roller 27.
Is provided. Another configuration of the image forming apparatus 1 of this example is as follows.
This is the same as the image forming apparatus 1 of the example shown in FIG.

In the image forming apparatus 1 of this embodiment configured as described above, the image carriers 2 _K , 2 _C , 2 _M , and 2 _Y of the respective colors are provided on the image carriers 2 _K , 2 _C , 2 _M , and 2 _Y similarly to the image forming apparatus 1 of the example shown in FIG. The developer images of the respective colors are formed, and the developer images of the respective colors are color-matched in the same manner as when the developer images of these colors are transferred to the intermediate transfer body 25 on the transfer material 5 in the example shown in FIG. Overprinted. The developer image of each color intermediately transferred to the intermediate transfer body 25 is transferred to the transfer material 5 by the transfer device 6, and the transfer material 5
, A full-color developer image is formed. Other image forming operations of the image forming apparatus 1 of this example are the same as those of the image forming apparatus 1 of the example shown in FIG.

As described above, the writing apparatus according to the present invention is also applicable to a full-color image forming apparatus having the intermediate transfer device 24 and having the image forming apparatuses 1 _K , 1 _C , 1 _M , and 1 _Y for each color arranged in tandem. By using 3, a more compact and simpler configuration can be achieved.

[0059]

As is apparent from the above description, according to the present invention, the contact between the electrode portion and the image carrier is stabilized, and uniform selective charge writing becomes possible. Image can be obtained. Further, it is possible to prevent the writing failure of the electrostatic latent image generated by the fogging toner remaining in the non-image areas at both ends of the developing means adhering to the writing electrode.

[Brief description of the drawings]

1A and 1B show an example of an image forming apparatus according to the present invention, wherein FIG. 1A is an overall configuration diagram, and FIG. 1B is a partial perspective view of an image carrier and a charge writing device of FIG. is there.

2A and 2B illustrate a principle of writing an electrostatic latent image by charging a writing electrode of the charging writing apparatus of FIG. 1; FIG. 2A is an enlarged view of a contact portion between the writing electrode and an image carrier; FIG. 2B is an electrical equivalent circuit diagram of the contact portion, and FIGS. 2C to 2F are diagrams showing the relationship between each parameter and the surface potential of the image carrier.

3A is a diagram illustrating charging of an image carrier by charge injection, FIG. 3B is a diagram illustrating charging of an image carrier by electric discharge, and FIG. 3C is a diagram illustrating Paschen's law; FIG.

FIG. 4 is a diagram showing an example of an arrangement pattern of write electrodes.

FIG. 5 is a diagram showing a switching circuit for selectively connecting a predetermined voltage and a ground voltage to a write electrode.

FIG. 6A shows a state when each high-voltage switch of each electrode is selectively switched to a predetermined voltage or a ground voltage, and FIG. 6A shows a voltage state of each electrode;
6B is a diagram showing a developer image when normal development is performed in the voltage state of FIG. 6A, and FIG. 6C is a diagram showing a developer image when reverse development is performed in the voltage state of FIG. 6A. FIG.

FIG. 7 is a diagram for explaining the problem of the present invention.
FIG. 7A is a perspective view showing an example of an image forming apparatus using a charged writing device, and FIG. 7B is a partial cross-sectional view of FIG. 7A.

FIG. 8 is a diagram for explaining a problem of the present invention, and is a diagram for explaining a width dimension of each member. It is a figure for explaining a subject of the present invention.

FIG. 9 is a diagram illustrating an embodiment of the image forming apparatus according to the present invention and illustrating a width dimension of each member.

FIG. 10 is a perspective view of FIG. 9;

FIG. 11 is a diagram illustrating an example in which the present invention is applied to an image forming apparatus using an intermediate transfer belt.

FIG. 12 is a diagram schematically showing another example of the image forming apparatus using the writing device of the present invention.

FIG. 13 is a diagram schematically showing another example of the image forming apparatus using the writing device of the present invention.

FIG. 14 is a diagram schematically showing another example of the image forming apparatus using the writing device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 2 ... Image carrier 3 ... Charge writing means 3a ... Base material 3b ... Writing electrode 3bR ... End electrode 4 ... Developing means 6 ... Transfer means

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuo Yoda 3-3-5 Yamato, Suwa City, Nagano Prefecture Inside Seiko Epson Corporation (72) Inventor Yujiro Nomura 3-3-5 Yamato Suwa City, Nagano Prefecture Seiko Epson (72) Inventor Shinichi Kamoshida 3-3-5 Yamato, Suwa-shi, Nagano Seiko Epson Corporation F-term (reference) 2C162 AE21 AE31 AE44 AE47 EA20 2H029 AA06 AB03 AB10 AB16 AD01 AD07 AE02

Claims (2)

[Claims] 1. An image forming apparatus for forming an electrostatic latent image on an image carrier by a charging writer having a plurality of write electrodes which are in contact with or close to the image carrier along an axial direction of the image carrier. The image bearing member contact width dimension of the charging writing means is L
1. The toner carrying width of the developing means facing the image carrier is L
2. The width of the image carrier is L0, and the width of the transfer means is L3.
Wherein L1 <L2 and L1 <L3 are satisfied. 2. The image forming apparatus according to claim 1, wherein a relationship of L1 <L3 <L2 is satisfied.